Neurons/Neurotransmitters WEEK 5 Flashcards
PNS
Periphereal Nervous System
The branches that come out off the axon are called
Axon Terminals
CNS
Central Nerous System
PNS contains
all neural structures that are outside the brain and spinal cord
Two main functions of the PNS
Input and out put functions
Input function of PNS
sense whats going on inside and outside the body
Output function of PNS
Allows you to react/response through muscles and glands
PNS- Somatic Nervous System SNS (part of PNS)
Ability to sense and respond to environment, mechanic in the body that allows that to happens
Make up of PNS
Somatic Nervous System PNS *****
The somatic nervous system contains sensory neurons
This study has moved away from looking at specific areas and now to
Networks
The brain is constantly producing —— even in adulthood and post debvelopment
cells
Neuron two main areas
Cell Body - soma
and the Axon
Neuron collect messages for the —- from neighbouring nurons
Soma
Genetic material in the nucleus of a neuron shapes —-
function
Insulating membrane controls the exchange of chemical substances in an out of the cell
Myelin Sheath
The centre of the soma or neuron is called the
Nucleus
The branch off the soma of a neron (insulated by the myelin sheath) is called the
Axon
Neurons require — to stay alive
biochemical structures
The branches that come out off the soma are called
Dendrites
Nueron axons conduct electrical impulses to
Other neurons/glands/muscles
Having many axon terminals allows a neuron to
permit a single neuron to pass messages to thousands of neurons
the transmission of neurotransmitters across the cell membrane can be measured and is important because it grants us the ability to use disgnostics such as
EEG etc in order to look at neural firing
Action potential is built up during
the transmission of neurotransmitters across the cell membrane
Action potential builds up and fires an impulses down the axon which allows for
interconnection between all areas of the brain
Nuerons are general local, they are not
long distance communication devices
most neurons talk to each other within a
hemisphere
Neurons are the
basic building blocks of the nervous system
Extimated 100 billion or trillion nueronsEsimated number of neurons we have is
upwards of 100 billion if not trillions
The cells that provide support for the neurons are called
Glial cells
Imagine a chocolate chip cookie, if the nurons are the chocolate chip the cookie is the
Glial cells
Glial cells
hold neurons in place, manufacture nutrient chemicals and absorb toxins and waste
Neurons generate —- and this creates ——- which ——-
Neurons generate electricity, and this creates nerve impulses (to fire action potentials down the line)
Neurons release chemicals that
facilitate communication and do various things
A neuron begins at —— resting potential
negative
The cell membrane of a neuron encloses
cytoplasm
The cytoplasm of a cell contains
Various Ions dissolved in it
neurons themselves are immersed in a salt solution called
Extracellular fluid
The ions of the cytoplasm consist mainly of positively charged potassium ions and large —– —— —– ——
negatively charged organic molecules (such as proteins)
Extracellular fluid contains
mostly positively charged sodium ions and negatively charged chloride ions
Unstimulated, neurons maintain a constant electrical difference or “potential” across their cell membrane called
resting potential
The potential called resting potential is always —- inside the cell
negative (-40 to -90 millivolts)
The negative potential inside the neuron can be made —– or —- negative depending on the —–
more or less negative depending on the stimulus
If potential is made less negative it reaches a level called
Threshold and an action potential is triggered
During action potential the neuron suddenly becomes
20 - 50 milivolts positive inside (lasting a few millisecond)
After action potential is triggered the
cell restores its negative resting potential
since chraged particles cannot pass through the lipids that make up cell membranes
they must travel through channel protiens that extend through the membrane
In an unstimulated neuron only —– ions can cross the membrane
potassium
potassium ions, travel through specfic protiens called
potassium channels
Although sodium channels are also present in unstimulated nureon they are
closed
since only potassium ions can cross the membrane and are more concentrated inside the call
they diffuse out ofthe cell, leaving the large organically charged ions behind
As the potassium ions leave the cell, the inside of the cell becomes increasing
negative
because opposite charges attract, as potassium ions an electrical force develops that tends to pull them
back inside the neuron
At some point the diffusion of potassium ions outside the neuron due to concentration difference is balanced by the electrical attraction tending to pull them back inside, this is the point at which neurons reach
Resting potential
Reaching resting potential in this way does not require significant changes in
potassium concentration inside or outside the cell (only about 1/10,000 of the potassium ions initially inside a neuron must leave to create a resting potential of -60 millivolts
action potentials (not resting potentials) do what:
carry information through a nervous system
3 steps in the Activations of nerve impulses (nuerall impulse/action potential)
- Electronic Resting potential
- Neuron is stimulated and Action potential occurs
- Original ionic balance is restored, and the neuron returns to resting potential
There is a —– period where the neuron is silent and wont fire again for a period of time or until the threshold is built up again
refractory
Neuron is seperated from surrounding fluid by a
cell membrane
Substances can pass through a cell membrane using designated
ion channels
Inner ions are more negatively charged than the
surrounding ions
When a neuron is at rest it is
negatively charged
Positive sodium ions enter a neuron causing brief
depolarisation
the action of positively charge sodium ions entering the call membrane and causing depolarisation between the negaively and positively charged ions is what we measure using
EEG for example
Action potential is
the electrical shift when a neuron is stimulated
Resting potential….sodium flows in …. causing depolarisation between negative and positive, which will affect or reach the
Action potential Threshold
Once the action potential threshold is reached this triggers an
Action potential
After an action potential threshold is reached and thus the action potential is triggered the ——- ions flow ou
the potassium ions flow out
After an action potential, the potassium ions flow out which causes
Repolarisation (of the ions)
After and action potential and repolarisation of the ions a neuron will have a brief
refractory period where it remains silent until restimulated
After an action potential and before a return to resting potential, the neuron will have a brief
refractory period then return to resting potential
An action potential usually occurs in what measure of time
millisecond
Action potential threshold begins to come into play as the
neuron depolarises (the charge builds up in the neuron, potassium ions enter)
the charge builds up in the neuron because
potassium ions enter
The neuron cannot fire until it regains natural negative resting polarisation, this is achieved by the
Absolute refractory period
All or none law of a neuron
Action potential occur either at a uniform (maximum) intensity or not at all. Binary. (if it doesnt build up past the threshold, it just returns to its resting state, it does not fire at all. You do not get a weak or stong firing, you get firing or no firing)
Can a neuron transmit a weak signal if it does not reach the action potential threshold
No, An action potential either fires or it does not. If the Action potential is not reach, nothing happens.
We can have a summation of graded potential (charge below action potential threshold) come together to reach
Action potential threshold - trigger an action potential
Any change to resting potential that doesnt reach action potential thershold is called
Graded potential
Rules of Nureons
All or none
Action potential Threshold
Graded potential
We can have grade potentials (any charge) coming together to summatie into
firing (in certain circumstances)
Stochastic / Stochaticity
the quality of lacking any predictable order or plan. haphazardness, randomness, noise, irregularity - not characterized by a fixed principle or rate; at irregular intervals.
the threshold is not neccessarily always the
same (either graded potentials can add up or the thresholds can change and thus whether a neuron fires or not can actually be seen as a probabilistic function)
——- ——- refers to a function or process that involves randomness or uncertainty in its outcomes. Often used to model complex and uncertain behaviors.
probabilistic functions
Whether a neuron fires or not may be viewed as a
probabilistic function ( a function or process that involves randomness or uncertainty in its outcomes, often used to model complex and uncertain behaviours.)
Bayesian probability
is an interpretation of the concept of probability, in which, instead of frequency or propensity of some phenomenon, probability is interpreted as reasonable expectation representing a state of knowledge or as quantification of a personal belief. (ie. Bayesian probability is like using your personal knowledge and beliefs to make predictions, taking into account the information you have at the moment. It’s a way to put numbers to what you think is likely to happen based on what you know.)
Neurons touch each other, true or false
False (neurons do not touch)
Axon terminals and dendrites (branches of the soma) do not touch the space between (small interstitial space) them is called the
Synaptic space
Chemical substances that carry messages across the synaptic space to other muscles, neurons or glands are called
Neurotransmitters
The axon has branches to send the messages called axon terminals and at the send of each of these axon terminals is a
synaptic terminal
The neurons get close to each other but do not touch one another, this space is called the
Synapse (or synaptic cleft)
There is a miniscule gap between the neurons called the
synaptic cleft
In a communication what is the first neuron that is passing the message called
presynaptic neuron
An axon terminal or synaptic terminal passes the message to a
dendrite (branch of the soma, neuron cell)
The neuron that receives the message is the
post synaptic neuron
The arrival of an action potential at the synaptic terminal causes the synaptic terminal to become
positively charged
Once a synaptic terminal is positively charged (due to the arrival of the action potential) which releases
neurotransmitters into the synaptic cleft (space)
Neurotransmitters diffuse rapidly across the
synaptic cleft (space)
When neurotransmitters are diffused across the synaptic cleft they then bind to the receptors of the membrane of the
dendrites (branches of the soma - or cell body) of the post synaptic cell (neuron)
Each type of receptor in the post synaptic membrane binds to a
specific type neurotransmitter
after binding to a neurotransmitter the
receptor causes
specific types of ion channels in the postsynaptic membrane to open
ion channels are opened, ions
flow across the cell membrane of the
postsynaptic neuron
As ion channels are opened, ions
flow across the cell membrane of the postsynaptic neuron along their
along their
concentration gradient
The flow of
ions into the postsynaptic neuron (across their conecentration gradients)
causes
a postsynaptic potential
The flow of
ions into the postsynaptic neuron (across their conecentration gradients) causes
a postsynaptic potential in the
in the dendrites or cell body of the post synaptic cell
depending on the
channel’s open and the ions that flow in
synaptic potentials can be either
Excitatory or Inhibitory
excitatory synaptic potentials
make a neuron less negative
inside and more likely to fire an action
potential
inhibitory synaptic potentials
making it more
negative and less likely to fire
EPSP
excitatory postsynaptic potential
IPSP
inhibitory postsynaptic potential
a synapse that produces EPSPs in the
postsynaptic cell is called an
excitatory synapse
the synapse
producing IPSPs is an
Inhibitory synapse
postsynaptic potentials cannot travel
far and in a neuron, after a few millimeters
at most, the ions
leak back across the
membrane and the signal is lost.
postsynaptic potentials travel
far enough to reach
the cell body (where
they determine whether or not an action
potential will be produced)
Once a post synaptic potential reaches the cell body they determine
whether or not an action potential will be produced (if the threshold is reached)
HOW NEURONS COMMUNICATE: STEP 1 synthesis
transmitter molecules are formed (they need to make a transmitter molecule to actually communicate)
HOW NEURONS COMMUNICATE: STEP 2 storage
Transmitter molecules need to be stored in synaptic vesicle (in the axon terminals)
HOW NEURONS COMMUNICATE: STEP 3 release
Action potential in one neuron triggers the release of transmitter molecules from the synaptic vesicles (across the gap/cleft)
HOW NEURONS COMMUNICATE: STEP 4 BINDING
transmitter molecules bind themselves to receptor sites which are large protein molecules embedded in the receiving neurons cell membranes. (lock and key)
Like a lock and key each neurotransmitter
fits in a specific receptor site in the next site
Psychopharmacutical drugs can block certain
neurotranmitters
Psychopharmacutical drugs can —– inhibit neurotransmitters
re-uptake inhibit neurotransmitters - (Reuptake - The reabsorption of a neurotransmitter by a neurotransmitter transporter located along the plasma membrane of an axon terminal (i.e., the pre-synaptic neuron at a synapse) or glial cell after it has performed its function of transmitting a neural impulse.)
The reabsorption of a neurotransmitter by a neurotransmitter transporter located along the plasma membrane of an axon terminal (i.e., the pre-synaptic neuron at a synapse) or glial cell after it has performed its function of transmitting a neural impulse.
Reuptake
HOW NEURONS COMMUNICATE: STEP 5 deactivation
Deactivation through reuptake or breakdown
Neurons are also known as —- —- and are the ————–
Nerve cells, basic units of the nervous system
we think, we feel, we hurt we want all through the silent processes of
Neurons
Neurons do what:
carry information from cell to cell within the nervous system as well as to and from organ muscles and glands
There are three types of neurons
sensory and motor neurons and interneurons
Transmit information from sensory cells in the body called receptors (cells that recieve sensory information) to the brain, about sensors perceived
Sensory Neurons
Sensory cells in the body
receptors
Output is received by these nerve cells that connect other neurons with one another. These take up the vast majority of neurons in the brain and spinal cord
Interneurons
receptor send information to the
brain
Transmit commands from interneurons to the glands and muscles (most often through the spinal cord)
Motor Nuerons
Motor neurons can carry out —– and —– actions
voluntary/involuntary
Sensory neurons are sometimes called
Afferent nuerons
Motor neurons are sometimes called
efferent neurons
The cell body includes a —– which contains the genetic material of the cell ( the chromosomes)
Neucleus
The axon of a neuron can be up to as long as
1metre
The function of the Axon is to transmit information to
other neurons
True or false Axons have two or more off shoots (collateral branches)
true
The myelin sheath is primarily composed of
lipids
The myelin sheath insulated the axon from physical and chemical stimuli which prevents
electrical impulses getting crossed
The insulation of the myelin sheath also increases the
speed of transmission of messages
babies have uncoordinated and slwo movements because
when we are born not all axons are myelinated. Transmitting impulses is slow and arduous
an example of a demyelinating disease is
MS multiple sclerosis (degeneration of the Myelin sheath, causing issues for the nerves to send messages)
At the end of an axon are
terminal buttons
Terminal buttons send a signal from a neuron to an
adjacent cell
connections between neurons occurs at the
synapses
Elsewhere in the nervous system . neurons may send signals directly to
glads or muscles (rather than to other neurons)
the interacting network that underlies underlies all psychological activity
Nervous system
Carry sensory information from the sensory receptors to the CNS
Sensory Nuerons
Transmit commands from the brain to glands and muscles
Motor Neurons
Connect neurons with one another
interneurons
Nuerons contain 3 parts
Cell body, Axon and dendrites
Neurons connect at the
synapse
At the synapse the the electrical charge from one neuron gets converted into a
chemical message (neurotransmitter)
When the chemical message (neurotransmitter) is released into the synapse it alters the electrical charge of
the next neuron (PostSynaptic Neuron)
When a neuron is at rest it is
polarised
A neuron is polarised when
Inside the membrane has a negative charge and the fluid outside the cell has a positive charge
Although we call it resting potential a neuron is never completely
at rest
even when a neuron is resting it is
naturally letting some chemicals in and keeping others out
What is the scientific expression of sodium
Na+
What is the scientific expression of potassium
K+
What is the scientific expression of Chloride
Cl-
A small atom or molecule that carries an electrical charge is called an
ion
A cell membrane typical IS or ISNT permeable to positive charged sodium ions
IS NOT
because sodium sodium ions cannot easily get through the cell membrane they tend to
accumulate outside the cell/neuron
The cell membrane IS or ISNT completely permeable to a variety of negatively charged protein ions inside the cell
IS completely impermeable
As a result of the membrane being completely impermeable to negatively charged protein ions inside the cell the electrical charge is usually:
more negative on the inside than the outside of the cell
We refer to it as potential because
the cell has stored up a source of energy, which has the potential to be used
At resting potential the difference between the negatively charged inside and outside the neuron is about
-70 milivolts
A volt is a standard measure of electricity and on millivolt is
one -thousandandth of a volt. So like a millimeter to a meter
hyperpolarisation occurs when
the electrical difference increases both inside and outside the cell
Voltage changes occur at the synapses along the neurons dendrites and the cell body and the then spread down the cell membrane like
ripples in a pond
Spreading voltage changes that behave like “ripples in a pond” are called
Graded potential
Graded potentials have 2 characteristics
Their strength diminished with distance and they are cumulative or additive
The shift of polarity in polarity across the membrane and subsequent restoration of the resting potential is called
Action potential
Depolarising the axon membrane means for a flicker of an instant the membrane is
totally permeable to positive sodium ions (from outside - the negative are inside)
When the positive sodium ions pour in to a depolarised membrane, it caused the inside of the cell to become
positive (for a moment)
The outpouring of the positive potassium ions (which has increased inside the cell due to depolarisation) causes the neuron to
to rapidly restore resting potential (polarisation)
The firing of a neuron is called
Action potential
action potential spreads down the axon to the
terminal buttons (axon terminals)
unlike a graded potential an action potential is not
cumulative or additive
Although action potentials seem more dramatic the prime mover behind psychological processes is
graded potential
Create new information at a cellular level by allowing the cell to integrate information from multiple sources (multiple synapses)
Graded potential
signal that can only pass along information already collected without changing it
Action potential
When a neuron is stimulated by another its cell membrane is either
depolarised or hyperpolarised
Na+ cannot enter, or is actively pumped out, the cell is negatively charged
Resting state
Na+ enters the call body making it less negatively charged
Depolarisation
after depolarisation caused by positive sodium (Na+) flowing in, then the ——– flows out returning the cell to depolarisation
positive potassium (K+)
Action potentional causes terminal buttons/axon terminals to
release neurotransmitters into the synaptic ceft
If the change in the axon voltage surpasses a threshold, the axon suddenly lets in a surge of
Na+ Positive Sodium
Depending on the facilitating or inhibatory nature of the neurotransmitter released, the voltage of the cell membrane receiving the message becomes
depolarised or hyper polarised and the process repeats
Within the terminal buttons/axon terminals there are small sacs that contain neurotransmitters called
Synaptic vesicles
Once in the synaptic cleft neurotransmitters bind with protein molecules called
receptors
When a receptor binds with a neurotransmitter that fits it - in both molecular structure and electrical charge - the chemical balance of the postsynaptic cell changes, producing a
graded potential - a ripple in a neuronal pond
Neurotransmitter that depolarises a postsynaptic cell making an action potential more likely
Excitatory Neurotransmitter
hyperpolarisation of the membrane (more negative and mor positive) reduces the likelihood a neuron will fire
Inhibitory Nuerotransmitter
True or false - A neuron can release more than one neurotransmitter
True - affecting the cells in which its connected in various ways
Some neurotransmitters are released into a specific synapse and
only affect the neuron at the other end
Some neurotransmitters have a wide radius of impact and
stay active for much longer, once released they find their way into multiple synapses where they can affect any neuron within reach with the appropraite chemicals in its membrane
researchers have discovered more than ——- chemical substances that can transmit messages between neurons
100
The effect of a neurotransmitter depends on the —– it fits
receptor
neurotransmitters can activated different receptors depending —— the receptor is —–
where the receptor is located
The impact of a neurotransmitter depends less on the neurotransmitter rather than the
receptor it unlocks
Some neurotransmitters can have an excitatory effect at one synapse and
inhibitory at another
excitatory NT, memory formation, synaptic plasticity and learning
Glutamate
Abnormanly High concentrations of glutamate is called
excitotoxicity
Inhibatory NT, particularly important in regulating anxiety
GABA
GABA
gamma-aminobutyric
Dugs such as alcohol and valium bind with the receptors of this neurotransmitter that tend to reduce anxiety
GABA
NT that has a wide ranging affect on the nervous system including thought feeling and motivation and behaviour, movement and decision making and may play a part in addiction and depression
dopamine
The blood-brain barrier results occur because large molecules have
difficulty entering because the cells in the blood-brain barrier are so tightly packed
NT involved in regulating mood, sleep, eating , arousal and pain
Seretonin
Decreased seretonin is related to
severe depression
Some anti depressants work by
increasing serotonin
Some NT can be boosted by external circumstances that arent pharmacuetical such as
exersize, sunlight, socialising, diet
Seretonin usually plays a —– role
inhibitory
NT involved in learning and memory
Acetylcholine
A study on patients with Alziehmers disease shows they had deplete
ACh Acetylcholine
NT that elevates mood and reduces pain
endorphins (endogenous morphine) within the body painkiller
Opium and morphine bind to —– receptors
endorphine
PNS contains
all neural structures that are outside the brain and spinal cord
PNS
Periphereal Nervous System
